1. Field of the Invention
Example embodiments include an electrophoresis device comprising a hole-containing structure and a method for fabricating the same. Example embodiments include an electrophoresis device that is capable of controlling optical properties by which electrophoretic particles are embedded into holes and comprises a hole-containing structure exhibiting inherent optical properties, and a method for fabricating the same.
2. Description of the Related Art
Electrophoretic display devices are one of flat panel display devices used in electronic books, etc. Electrophoretic display devices comprise charged particles placed between two substrates, where an electric field-generating electrode is formed. When a voltage is applied across the two opposite electrodes, the particles are migrated toward the electrode bearing the opposite charge from that of the particles, thereby representing an image.
Since electrophoretic display devices have superior reflectivity and large contrast ratios, are free from dependency of a viewing angle, unlike liquid crystal displays, and are bistable, they maintain image representation even without continuous application of a voltage and thus enable low power consumption. In addition, electrophoretic display devices need no constituent component such as a polarizing layer, an alignment layer and liquid crystals, thus being considerably advantageous in terms of price competition.
FIG. 1 is a schematic view illustrating the structure and driving principle of a conventional electrophoresis device. Referring to FIG. 1, white (7W) and black (7B) charged particles 7 are fed to the space between two parallel substrates (i.e. an upper substrate 1 and a lower substrate 4), including a conductive electrodes 2 and 5, respectively. The two particles are oppositely charged and are thus separated to opposite substrates according to an applied electric field. As shown in FIG. 1A, in a case where the white particles (7W) are negatively (−) charged and the black particles (7B) are positively (+) charged, when a negative voltage is applied to the upper substrate, the black particles (7B) and the white particles (7W) are adsorbed on the upper substrate 1 and the lower substrate 4 bearing the positive charge, respectively. Thus, when a white light 9 is introduced from the outside, the black particles 7B absorb the incident light 9 and thus reflect no light. For this reason, an observer notices a black light. In an opposite case, the white particles (7W) are adsorbed on the upper substrate 1 and reflect all incident lights, thereby allowing the observer to notice a white light.
However, in the prior arts, the use of positively- and negatively charged particles makes it difficult to realize a desired reliability and driving of the device. FIGS. 2A and 2B are schematic views illustrating problems associated with a particle migration mode of a conventional electrophoresis device. Referring to FIG. 2A, white (7W) and black (7B) particles, oppositely charged, are in contact with each other and neutralized due to inherent electric attraction therebetween, regardless of the type of an applied driving electric field. As a result, the particles lose their charges and can thus no longer be driven by the electric field.
To prevent such a phenomenon, each charged particle may be capped with an insulating film, or deprived of its electron giving/taking function with the use of particle characteristics. Although charged particles are capped with an insulating film, there exists the electric attraction between the particles. Thus, two particles are in contact with each other to form a dipole, as shown in FIG. 2B. The formation of this dipole causes an undesirable increase in driving voltage since a driving electric field high enough to break the dipole and allow the particles to migrate must be applied across the substrates.
In an attempt to solve the afore-mentioned problems, an electrophoresis device, in which a barrier rib is formed, was suggested, as shown in FIG. 3. Referring to FIG. 3, an electrode 1 is arranged on either an upper substrate 1 or a lower substrate 4 and a counter electrode 5 is arranged on a barrier rib 10. Positively-charged black particles (7B) and a white reflective layer 11 are arranged above and under the lower substrate 4, respectively. When an electric field is applied to the device, the black particles (7B) are adsorbed on the upper substrate 1 and absorb an incident lights thus allowing the observer to notice a black light. On the other hand, when an electric field bearing the opposite charge is applied to the device, the black particles (7B) are adsorbed on the barrier rib 10. Thus, an incident light passes through the device and is reflected by the reflective layer 11, thus allowing the observer to notice a white light. Reversely, the device may be driven by using a black reflective layer and white particles, instead of the white layer 11 and the black particles, respectively. However, the device having the structure and driving principle involves the necessity of the barrier rib and has the difficulty of forming the electrodes on the barrier rib.